Conversion of iron-carbon alloys into products of sheeted and other shapes



Patented July 20, 1937 UNITED STATES 2,087,765 f 1'1' 1. CONVERSION FIRON-CARBON ALLOYS INTO PRODUCTS- OFc SHEETED AND OTHER SHAPES NathanH.""Schermer," Youngstown, as-

signor to Stellum, Inc., Cleveland, jQhio, a f

corporation of Ohio ,No Drawing. Application February-1 7:

Serial No. 657,258 v 7 v 20 Claims. (01.148142).

This invention relates in general to the treatment of cast iron-carbonalloys, particularly white cast iron, for the obtaining of products insheeted or other shapes with tensile strength and machinability,corrosion resistance, etc. as good or better than customary in malleableiron.

For the manufacture of malleable iron castings, it has been customary tosubject the-,iwhite iron castings, which contain carbon in the 1combined form, 1. e. cementite and pearlite, and whichv makes the metalhard and brittle, to a suitable heating or annealing treatment, therebychanging the combined carbon to an amorphous free carbon in the form oftemper-carbon, the metal becoming ductile, and known as malleable castiron. The annealing treatment usually consists in slowly heating thecastings to a temperature of about 1500 F., maintaining them at thistemperature for about fifty hours,-

and then cooling them very slowly. This an-. nealing treatment changesthe character of the castingfrom one having a white silvery crystallinefracture, in which no-graphite flakes are visible to the naked eye, toone having a dark gray, soft, velvety appearing fracture, in which thecarbon has been precipitated or segregated into rounded masses, leavinglittle or no carbon combined with the iron. This change takes place at atemperature as low as 1250 F., but'occurs more efiectively at atemperature of 1350F. The ordinary commercial temperature range "for thetreatment is from about 1250 F. to about 16'0oe F. This change incharacter of the metal is accompanied by a considerableincrease instrength manufacture of similar articles by stamping and otherfabricating methods, and is moreover. at-

tended with dimcultieswhich are not encountered in ordinary stampingpractice. In the manufacture of malleable iron castings for automobilebrake drums, for example, only the most highly skilled foundries can berelied upon to .produce 5 sound castings, with a minimum of rejections.-

Due to shifting of the patterns in the'mold, the" sections of thecastings are usually heavier than desired in the finished brake drum,and the ex-- cess metal is then required to be removed by slow 5 andexpensive machining operations. Moreover,

certain defects, inthe castings, which become visible only after,machining, such- .as porosity; shrinks ,and cold shuts, result inrejections in addition to those resulting from theinitialcastlng'operations. I 4 g It is among the objects of this invention accordingly,to provide advantageous processes fordirectly working iron-carbonalloys, such as white iron castings, preferably by rolling, and.subsequently annealing on the order of malleabilizing,v 10 orbymalleabilizing and subsequently rolling, and. in either. caseobtaining products of marked ductility, tensilestrength, resistance tocorrosion, etc., as contrasted with the initial cast iron.:'-.A furtherobject is the-production of such modified, 15 metalin the form ofsheets, strip, bars, tubes, and v other shapes, suitable for useassuch,wor for. stamping or fabrication into other products. Otherobjects'and, advantages, will appear-as the. I a description proceeds. i2

To the accomplishment of the foregoing and -f related ends, saidinvention, then, comprises the" features hereinafter fully described,and pa-rticularly pointed out inthe claims, the following descriptionsetting forth in; detail certain illus-. 25 trative embodiments of. theinvention, these be-; ing indicative, however, of but a few', ofthevarlous ways in whichthe principle of theinvention, may. be-applied.a In accordance with my invention, a melt is ;30 prepared and is castinto ingots, slabs, or forms as desired; For the composition of the meltsome latitude is permissible; :however, in general, it is desirablethat-the carbon be in the amount of from about, 1.50 to about 4.00. percent, silicon 35 from about 0.45 to about 1.75 per cent, manganesebelowl per cent, phosphorus not exceeding 0.225 per centand desirably under0.05 percent and suiphur'desirably notyexceeding 0.05- perucent.

Optionally also, I may add alloying metals, as40,

for instance molybdenum in amounts up to 1 per cent, 0.5 per. centgiving in general excellent: rea sults copper inv amounts up to 0.6 percent, etc.

The form and dimensions of the molds may, of course, vary in accordancewith the particular further purpose in view. For instance, for stripmill and universal mill work, it isldesirable \to' cast in slabs ofabout 3 inches thickness, "the width being dependent upon the width ofultimatesheet product desired, for instance 12 to 36 inches. For sheetmill rolling slabs. of -approximately inch' thickness are desirable. v

If the ingots or slabs are to be rolled without being previously*malleabilized, I: prefer where possible, tojiroll-them before theyghavecooledfl,

.down to an appreciable extent. For this purpose, they may be placed ina soakingpit or furnace wherein they are maintained at a temperaturesuitable for rolling, i. e., from about 1600 F. to about 2100 F. Byrolling the ingots or slabs before they have cooled below about 1800 F.,primary graphitization or malleabilization is avoided, and reheatingbetween passes is avoided. Where it is not feasible to thus soak theingots or slabs for rolling, they should be cooled or chilled as quicklyas possible to prevent mecipitation of graphitic carbon, 'arid'this maybe accomplished by positive chilling with exposure to circulating air,'as distinguished from mere passive cooling .down as heretoforepracticed. When these ingots or slabs are to be worked or rolled, theyare first heated to a suitable temperature 1200" F.2100 F. and mostdesirably about 1600 F.2000 F. It is advisable to roll above 1200 F., onaccount of greater plasticity and economy in rolling at the highertemperatures. Where reheating between passes is necessary on account ofthe size of the piece, etc., reheating temperatures to about 1500 F.2000F.

are usually preferable, although slightly" lower temperatures give goodresults. With a 3 inchwhite cast iron slab' as the 1starting material,and heating to about 1500 F., I have satisfactorily rolled down to athickness for instance of 0. 16 inch in six passes. It is advisable inheating,'not to heat too long and cause precipitemperature furnace, inwhich rapid heating up to about l500 F.-2000 F. which then requires arelatively short time, may be effected, and the I slab fed to the rolls.

After the iron is worked or rolled down as desired, it is subjected to aheating-or anneal-' ing, somewhat on the order of malleabilizing.

Desirably, this heating is carried on with the temperature around 1500"to 1550" F. for a period of time depending upon the thickness of thematerial, and then the temperature may be slowly lowered to about 1200F., whereupon it is desirable to then cool rapidly by removing from thefire and air-chilling. This gives a' better control of the grain-size ofthe ferrite and also makes possible obtaining of a more roundedcharacter in the temper-carbon grains.

.By adding molybdenum to the melt initially, I have found that theannealing or malleabiliz-' ing treatment proceeds muchimore rapidly, andthe time may be cut down accordingly. For instance,-with stock otherwiserequiring about hours heating, with theincorporation of 0.25

percent of molybdenum in the melt, a heating The slabs may be ing. Thisgives a better control of the grain size of the ferrite and makespossible obtaining of a more rounded character in the temper-carbon.

The ingots, slabs or other forms thus malleabilized, are. then reheatedfor working or rolling, being first heated to a suitable temperature,1000 F.-2000 F., and most desirably about 1000 F.-1600 F. Upon examininga section of the metal under the microscope after rolling, it .will beobserved that the metal resembles wrought iron in appearance, that is tosay, the black rounded masses of temper-carbon have .been elongated inthe direction of rolling and flattened in the same manner that the slaginclusions in wrought iron appear elongated and flattened. The ferritegrains also appear distorted, as in wrought iron.

Sheets andother'stock produced by either of the methods which have beenoutlined can be employed for fabricating if desired, or can be furtherfinished by cold-rolling. A final annealing at a temperature above 1200F. is advantageous' after cold working."

Following such annealing treatment, the products are in a condition inwhich they can be readily stamped-or otherwise fabricated into variousarticles, including a great" number which have heretofore beenmadechiefly in theform of malleable iron castings.

Sheet stock rolled and annealed in accordance with my process has-a'superior resistance to corrosion as compared with sheet steel, and lendsitself particularly to usage in exposed 1ocations. If desired,galvanizing or tinning, etc., may also be applied. 'On account of theproperties of my materiahnitriding is especially feasible and as shapedinto desired articles, it may be thus hardened or nitrided by heatingwith ammonia, along known or practical lines.

It will be understood that various products, in addition-to thosestated, may be made from the iron-carbon alloy slabs or ingots and thatvarious articles, in'addition' to those described, may be made from suchproducts. In making tubes, for

example, the-roller sheets may be slit into strips (skelp), which areshaped into cylindrical form, welded and annealed; or the slabs oringots may be rolled directly into skelp; which may be shaped intocylindrical form while hot, welded by well known electric weldingprocesses and annealed, the annealing in either'case being optional. v

While certain temperature ranges for working or rolling have beenspecifically set forth, it will be understood that the rolling may beconducted at temperatures other than those set forth. In

general, the working or rolling may be carried but below that atwhichthe metal loses its malle'-' ability, due to overheating.

While the term malleable iron" has been ap-" plied to products such aspure ,or puddled iron, and softor mild steels, which are admittedlymalleable in various degrees and in a greater degree than malleable castiron, such designation is entirely improper in the metallurgy of ferrousproducts, and it is therefore desired to particularly point out that theterm malleable iron as used and contemplatedin the specification andclaims is intended to mean malleable cast iron, which is a product onlyslightly malleable at ordinary temperatures, but is tougher than thecast iron from "which it is made. The term. malleable, as employed inthis connection is intended to designate a relative condition betweencast iron, which is practically devoid of malleability and malleablecast iron.

The term white cast iron, as used in this application, is intended todesignate an iron-carbon alloy which is within the melt analysis setforthin the specification. While it usually contains from about 2.00% toabout 3.00% carbon and from about .45% to about 1.75% silicon, it may.j. means and the steps herein disclosed, provided those stated by any01 the following claims or their equivalent be employed. v t

I thereforeparticularly point out and distinctly claim as my invention:

1. The method which comprises hot rollin graphitizable white cast ironcontaining a graphitizing agent.

2. The method which comprises 3. As a new article of manufacture, aproduct formed'by hot rolling graphitizable white cast iron.

4. The method which comprises plastically 'dforming into products ofsheeted and other shapes, j at a temperature above about 1200 F.,iron-carbon alloys containing more than 2.00% and up to about 4.00%carbon and a graphitizing agent in an amount sufficient to permit thealloys tobe 40 -grapl'n'tized after deformation, and then graphitizingsaid alloys.

5. The method which comprises hot rolling a ferrous alloy containingmore than 2.0% of carbon, and a graphitizing element in an amountsufiicient to permit graphitization of the alloy, and thereafter heattreating the alloy within the graphitizing range to precipitatesubstantially all of the combined carbon as graphite.

6. The method which comprises hot rolling,

white cast iron containing a graphitizing agent, and thereafter heattreating the same within the graphitizing range to precipitatesubstantially all of the combined carbon as graphite.

7. The method which comprises hot rolling white cast iron containing agraphitizing agent and then malleabilizing ,the same.

' 8. The method which comprises making graphitizable white ironcastings, subsequently heating the same to above about 2000 F. androlling. 9. As a new article of manufacture, a rolled whollygraphitizable iron-carbon alloy containit ing in excess of 2.00% carbon.

10. The method which comprises hot rolling white cast iron containingmore than 2% and up to about 4% carbon and a. graphitizing agent inrollingwhite cast iron containing a graphitizing agent at a temperatureabove about 1200 F. and then malg leabilizing the same.

an amount sufficient to permit graphitization of... the product afterrolling.

11. The method which compri'seshot rollingv white cast lron'containingmorethan 2% and up to about 4% carbon anda graphitizing agent in anamount suflicient to" permit graphitization of the product afterrolling, and then graphitiz ing the rolled product. I

12.'The method which comprises hot rolling graphitizable white ,cast 3iron containing more than 2% and up toabout 4% carbon and from about.45% to about.1 .75%- silicon.

13. The method .whichcoi'nprises' hot-rolling white cast ironc'ontainingmore than 2% and up to about 4% carbon, from about .45%'toabout then graphitizing the'productof said rolling.

14.v Asa new article-of manufacture;' a jprod 1.75% silicon, and'le'ssthan 1% manganese, and

uct formed byhotrolling white cast iron containing more than 2% and-upto about4% fcarbon rolling.

15. Asa new article of manufactura aiijprod- 4 uct formedby hot rollinggr'aphitizablef'white cast iron containing morethan 2% and up to' about4% carbonandfromabout .45 to about 1.75% silicon.

16. As a new article of manufacture, a prod uct formed by hotrollinggraphitizable white cast ironcontaining' morel-than 2% and up .to about4% carbon, from about .45%- to about' l.7 5%

silicon, and less than 1% manganese.

17. Themethod which comprises {plastically deforming into products ofsheeted and other 'white cast iron containing more than 2% and .up

shapes,at a temperature above about 1200F to about 4% carbon and agraphitizing. agent in an amount sufiicient to permit the product to .be

graphitized after deformation, and then graphitizing said product." t a18. The'method which comprises hot rolling.

white cast iron containing more than 2.0% of carbon, and a graphitizingelement in an amount suificient to permit graphitizationofthe product,and thereafter heat treating the product within the graphitizing rangeto precipitate substantially all of the combined carbonas graphite.

19. The method of making ferrous'articles comprising forming anarticleby hotworkingan ingot of an iron-carbon alloy containing :notless than about 1.5% of -carbon andals'o containing silicon andmolybdenum, as graphitizing elements, and the remainder of the alloybeing effectively iron, and heating the article at a temperature aboveits critical temperature to con vert a substantial proportion oi itscarbon content to the graphitic state.

20.. The method which comprises hot 'rolling a ferrous alloy containingbetween about 2.1 and} 2.5% carbon and about .9% silicon, andthereafterheat treating the alloy within the graphitizing bined carbonas'graphite. H I

NATHAN H. SCHERMER.

range to precipitatesubstantiallyall the com-f and a graphitizingagentin an amountsufficient [to permit graphitization of the productafter

